As the use of digital data increases, the demand for faster, smaller, and more efficient memory structures increases. One type of memory structure that has recently been developed is a crossbar memory array. A crossbar memory array includes a first set of conductive lines which intersect a second set of parallel conductive lines. Programmable memory elements configured to store digital data are placed at intersections between the first set of lines and second set of lines.
Creating higher density memory arrays has traditionally been accomplished by reducing the width of the conductive lines and the size of the memory elements. However, smaller line widths and smaller memory elements lead to more expensive and complicated manufacturing procedures.
One method of creating higher density memory arrays is to stack the crossbar arrays in a third dimension. However, stacking the crossbar arrays require more masks in the photolithographic processes typically used to manufacture the crossbar arrays. The more masks which are used, the more expensive it is to stack memory arrays in the third dimension.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.